1. Field of the Invention
The present invention relates to an Internet facsimile apparatus and an Internet facsimile communication method.
2. Description of the Related Art
In recent years, an E-mail Internet facsimile apparatus (hereinafter referred to as IFAX), which performs data transmission/reception over Internet using e-mail, has been in practical use as disclosed in, for example, Unexamined Japanese Patent Publication No. 8-242326 and the corresponding U.S. Pat. No. 5,881,233.
In a general IFAX communication system, an e-mail message transmitted from an IFAX at a sender side is sent to a mail server on a receiver side via a mail server on the sender side. In the case of POP3, the e-mail message is stored to the mail server, and a receiver terminal inquires of the mail server whether or not the e-mail message is arrived at the mail server at a fixed time interval to receive the e-mail message from the mail server. In the case of SMTP, when the mail server receives the e-mail message from the mail server, the mail server directly distributes the received e-mail message to a receiver terminal. Unlike the case of POP3, the receiver terminal does not have to inquire of the mail server.
The IFAX communication system has advantages in which (A) image information is transmitted using the Internet, making it possible to largely reduce a communication cost as compared with a normal G3/G4 facsimile communication system, and (B) the use of e-mail transfer protocol (SMTP, POP3, and so on) makes it possible to perform communication, which passes through an Internet firewall.
However, in the e-mail system including the IFAX communication system, a plurality of mail servers distributes by turns the e-mail message from the sender to a final distribution destination as relaying. Therefore, distribution time depends on mail server processing time, operation state, and the like. For example, when an abnormal overload is applied to a certain mail server at a relay point, it takes several hours before the message is distributed to a next relay point in some cases. Moreover, when the power supply of the mail server temporarily drops, re-transmission to the mail server is repeated, causing the e-mail distribution to be delayed by an amount of time, which is required before the power supply starts up, in some instances. Thus, in the IFAX communication system, since there is a possibility that delay in the delivery of e-mail message will occur, a real-time property is not insured.
Furthermore, in the IFAX communication system, it is proposed that IFAX on a receiver side notifies a sender of an e-mail message (delivery status notification mail; DSN, proposed in RFC of IETF) for informing the sender of a delivery status of transmitted e-mail message. Moreover, in the normal e-mail system, when a destination mail address is incorrect or a mail server on a receiver side goes down, such an operation that a mail server on a sender side transmits an error mail to the sender is carried out. When IFAX on the sender side receives the delivery status notification mail from the destination or the error mail from the mail server, hereinafter referred to as “delivery confirmation mail”, the mail is printed and the content is notified to the sender.
In this way, failure in transmission can be recognized. However, even if the delivery confirmation mail is used, image information does not reach a communication partner unless the sender performs re-transmission. In view of this point, the real-time property is not insured in the IFAX communication system.
In a G3/G4 facsimile communication system, since communication is carried out as performing negotiations with each other, the real-time property is insured. Even in the IFAX communication system, it is strongly desirable that the real-time property be insured as making use of the advantages of e-mail.